For products all over from industrial apparatuses to home electronics/information terminals, semiconductor devices for electrical power are becoming widespread, and with respect to the semiconductor devices for electrical power to be installed in the home electronics, they are required to have high productivity and high reliability that allow them to deal with a wide variety of products as well as to be made compact and lightweight. At the same time, they are also required to have a package configuration that is applicable to silicon carbide (SiC) semiconductors which are highly likely to go mainstream in future because of being high in operation temperature and superior in efficiency.
In semiconductor devices for electrical power, because they deal with a high voltage and a large current, it has been general to wire a plurality of bonding wires each made of aluminum, etc. and being thick up to φ0.5 mm, for example, to a main electrode on the front face side of each of their semiconductor elements for electrical power, to thereby form an electric circuit. In contrast, for the purpose of improving productivity, etc., a semiconductor device for electrical power in which a wiring member formed of a metal plate such as a lead frame and the main electrode are bonded together by use of a solder, and a semiconductor device for electrical power in which a wide-width aluminum ribbon is ultrasonically bonded to the main electrode, are becoming widespread.
The aluminum ribbon has a larger cross section as compared with the bonding wire, thus making it easy to increase the current capacity while enhancing the productivity. However, when its length becomes long, heat generation becomes large like the bonding wire. For that reason, it is unable to be drawn out from the main electrode directly to the outside and thus, is required to be connected to an external terminal using a bus-bar made of copper, through a connection, with a ceramic board. This results in enlargement of the ceramic board and thus, the cost increases; in addition, the module becomes large as a whole, so that there is concern that thermal stress due to a difference in thermal expansion coefficient between the metal member and another also increases, thus adversely affecting reliability even in the bonded portion. Meanwhile, in the case of using a brazing material such as a solder, because the surface electrodes of semiconductor elements are mostly made of aluminum, it is necessary to metalize a surface of the main electrode with a metal bondable to the solder by copper or nickel plating processing or the like, resulting in complicated processes.
In this respect, there is proposed a method in which a clad ribbon formed in an arch shape is bonded by ultrasonic bonding onto the main electrode, and is bonded by soldering to an electrode plate (for example, Patent Document 1).